There are many different kinds of texts such as dictionaries, encyclopedias, guides, and other sources which can help you find new items. These 'guides' can help you determine historical context, useful keywords to try in database searching, or other subject areas which cover your topic. Here are a few suggestions to browse; remember that the table of contents and index in each book will be quite helpful as well.
Hamilton Main Reference E169.12.A419
A nine-volume work on American history and culture, with one volume for each decade; series covers 1900-1989. Each volume is divided into thirteen segments, each segment covering a different facet of American history. Examples include World Events, Education, Religion, Science and Technology, and others.
Congressional Quarterly's Guide to the Presidency
Hamilton Main Reference JK516.C67 1996
Comprehensive encyclopedia containing information about the origins, history, and present operation of the U.S. presidency; appendices include cabinet members for each administration, and other information.
Dictionary of American History
Hamilton Main Reference E174.D52 1976
An eight-volume work with two supplements, contains articles covering every aspect of American history, with the exception of biography
Encyclopedia of American Economic History
Hamilton Main Reference HC103.E52
A three-volume work containing roughly 95 essays on various aspects of the economic life and history of the United States, current as of 1980.
Encyclopedia of Multicultural America
Hamilton Main Reference E184.A1 G14 1995
A two-volume work containing short profiles of virtually every ethnic group residing in the United States; profiles include history, reasons for emigrating, culture and traditions, and more.
Encyclopedia of race, ethnicity, and society
2008 Sage publication - online only
Harpercollins Dictionary of American Government and Politics
Hamilton Main Reference JK9.S43 1992
A one-volume work containing definitions of over 5,000 words and phrases relating to U.S. government and politics on all levels from local to federal.
Oxford Companion to American Literature
Hamilton Main Reference PS21.H3 1995
A one-volume work detailing various aspects of American literature, including prominent authors, works, movements, etc.
Worldmark Encyclopedia of the States
Hamilton Main Reference E156.W67 1995
An encyclopedia of the 50 states, including individual segments on Puerto Rico and the District of Colombia; covers history, geography, demography, economy, and social aspects, current as of 1995.